WHOLE GRAIN DIETS REDUCE BLOOD PRESSURE IN MILDLY HYPERCHOLESTEROLEMIC MEN AND WOMEN

Authors: Behall, Kay; Scholfield, Daniel; Hallfrisch, Judith

Submitted to: Journal Of The American Dietetic Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2005
Publication Date: 9/1/2006
Citation: Behall, K.M., Scholfield, D.J., Hallfrisch, J.G. 2006. Whole grain diets reduce blood pressure in mildly hypercholesterolemic men and women. Journal Of The American Dietetic Association. 106:1445-1449.

Interpretive Summary: Hypertension has been reported to be an independent promoter of vascular damage and is present in about 50 million in the US. As the population ages, the prevalence of hypertension appears to increase. The metabolic syndrome, a cluster of factors that includes hypertension, abdominal obesity, elevated plasma glucose and/or insulin, insulin resistance and dyslipidemia is increasing with the rise in obesity in the US. Consumption of diets high in whole grains or soluble fiber has been reported to have beneficial health effects on many of the factors associated with the metabolic syndrome. This study investigated whether consumption of barley would reduce the risk factors, including blood pressure, comparable to reductions observed with other soluble fiber sources. Moderately hypercholesterolemic subjects (women and men) consumed a controlled diet containing 30% of the energy from fat and no more than 300 mg dietary cholesterol for 17 wk. After a 2 wk adaptation period, whole grain foods containing 0 (whole wheat and rice), 3 g (50/50 mix of the grains ), or 6 g (barley alone) soluble fiber/day from barley were included in the diets consumed for 5 weeks each. Blood pressure was determined weekly before breakfast. Urinary excretion of Na, K, P, Ca, Mg, uric acid, creatinine, urea nitrogen, and glucose were determined from 72-hr urine collected at the end of each diet period. From initial measurements, systolic, diastolic, and mean arterial pressure (MAP) did not change during the equilibrium diet but were significantly lower at the end of the study (5.6%,7.5% and 8.4%, respectively). Systolic pressure was lower after the wheat/rice and ½ & ½ diets. Diastolic and MAP were reduced by all of the whole grain diets whether the fiber source was predominantly soluble or insoluble. No significant differences were observed in any of the urinary metabolites or minerals among the diets. Increasing intake of total dietary fiber in a healthy diet through whole grain foods, whether high in soluble fiber (barley) or insoluble fiber (wheat and rice) can reduce blood pressure. This information is important to the general public and to health care workers planning diets for individuals with hypertension or the metabolic syndrom since it increases the number of grains that can be consumed for beneficial reduction or control of blood pressure.

Technical Abstract: Objectives: The objective of this study is to compare the effects of predominantly insoluble fiber grains (whole wheat/brown rice) & soluble fiber grain (barley) in a whole grain diet consumed by men, premenopausal and postmenopausal women on cardiovascular risk factors. Subjects: Twenty-five normotensive subjects (7 men, 9 premenopausal and 9 postmenopausal women) with mildly elevated total plasma cholesterol levels completed the study. Design: Subjects consumed a controlled Step 1 diet (30% fat, 55% carbohydrate, 15% protein, < 300 mg cholesterol). After the 2 wk equilibration period, subjects consumed diets in which about 20% of energy was replaced with whole wheat/brown rice, barley, or ½ barley & ½ whole wheat/brown rice for 5 wk each in a Latin square design. Main outcome measure: Blood pressure was determined weekly before breakfast. Urinary excretion of Na, K, P, Ca, Mg, uric acid, creatinine, urea nitrogen, and glucose were determined from 72-hr urine collected at the end of each diet period. Data were evaluated with mixed procedure analysis of variance. Results: From initial measurements, systolic, diastolic, and mean arterial pressure (MAP) did not change during the equilibrium diet but were significantly lower at the end of the study (5.6%,7.5% and 8.4%, respectively). Systolic pressure was lower after the wheat/rice and ½ & ½ diets. Diastolic and MAP were reduced by all of the whole grain diets whether the fiber source was predominantly soluble or insoluble. No significant differences were observed in any of the urinary metabolites or minerals among the diets. Conclusion: Increasing whole grain foods in a healthy diet can reduce blood pressure.